292 



EMBRYOGENESIS IN PLANTS 



Cytological disturbances and somewhat comparable polyembryonic 

 developments have been observed in Alnus rugosa (Fagales : Betulaceae) 

 by Woodworth (1930) and in Atraphaxis frutescens (Polygonaceae) by 

 Edman (1931). In the latter species, where both micropylar and 

 chalazal embryos were formed, the latter usually degenerated. In 



Fig. 81. Further examples of polyembryony 



A, Potentilla aiirea (after Lebegue). B, Crepis capillaris (after Gerassimova). C, 

 Sagittaria graminia (after Johri). D, Spathiphyllum patinii (after Schurhoff). E, 

 Bergenia delavayi (after Lebegue). F, Arabis lyallii (after Lebegue). G, Lobelia 



syphilitica (after Crete). 



Elatostema spp., a multiple-origin polyembryony is also found 

 (Fagerlind, 1944), Fig. 80f, h. Closely contiguous embryos sometimes 

 fuse and form complex tissue masses. As ovum, synergid, antipodal 

 and nucellar embryos tend to become aligned in the embryo sac axis, 

 an ovum and an antipodal embryo may thus have their cotyledons 

 directed towards each other. 



The importance of the cytological and genetical aspects of poly- 

 embryony is well illustrated in some species with twin and triplet 



